On a day-to-day basis, materials are commonly described as solids, liquids or gases; however, many commercially important products possess characteristics that are intermediate between those of an ideal solid and an ideal liquid. They are referred to as “viscoelastic materials,” whose physical characteristics are somewhat temperature dependent; they may be described as viscoelastic solids (solid-like behavior dominates) or viscoelastic liquids (liquid-like behavior dominates). The present disclosure focuses on materials that are viscoelastic solids under ambient conditions.
Viscoelastic solids are manufactured and supplied in a wide variety of physical forms, such as particles, flakes, fibers, granules, lozenges, pills, pellets, pastilles, prills, strings, ropes, filaments, troche, tablets or other forms dependent on the nature of the material and its end-use. During manufacturing, a molten or liquid material is converted to a viscoelastic solid, generally by cooling to ambient temperature. Agglomeration or blocking of the resultant viscoelastic solid product is a common problem during subsequent handling, processing, storage and transport.
Significant compressive forces between individual particles may be generated as a result of:                1. The mass of material within bulk storage or handling systems.        2. The mass of material within an individual package, as in a bag, drum, bin or box.        3. Stacking bags or other compressible containers of the product on top of each other, as on a pallet or in a warehouse.Under such conditions, individual particles tend to adhere to one another, converting it from an easy-to-handle, easy-to-process, free-flowing particulate to an agglomerated mass resulting in a “blocked” product. Reduced efficiencies and added costs are a direct consequence of this agglomeration.        
Blocking becomes more pronounced with increasing duration and magnitude of the compressive forces as well as increased temperature. Thus, using temperature-controlled conditions during storage and transport minimizes the problem, but increases costs to the producer and end-user.